In copending application Ser. No. 09/645,828, filed Aug. 25, 2000 and entitled xe2x80x9cGUSSETED ZIPPER BAGxe2x80x9d a gusseted reclosable bag is disclosed in which portions of the gusset walls are captured between the zipper profiles. Such gusseted zipper bags have the feature that mating elements of zipper, when they are closed, capture between them portions of the gusset wall which are thinner than the remaining gusset wall thickness. This may be done by thinning these areas or by forming spaced-apart cutouts or windows in the web areas which are subsequently sealed over with segments of film that are thinner than the original film.
During various manufacturing steps in the formation of reclosable bags the zipper needs to be kept closed or the zipper profiles may lose their precise alignment and then not mate properly on re-closing. However, in the formation of the above described type of gusseted reclosable bags the two opposite ends of the zipper profile need to be open and spaced apart during the final manufacturing stage when the thinned out areas of the side gussets of the bag are tucked in between the zipper profiles.
This invention pertains to a method and apparatus for preparing a film web to be used in the a vertical form fill and seal (VFFS) manufacture of such gusseted plastic zipper bags. More particularly, this invention concerns separating the profiles at the ends of a zipper strip and attaching such open-ended zipper transversely across the film web and in the method of making reclosable bags from the web with attached zipper.
In view of the above a principle object of the present invention is to provide a method and means to open the ends of a segment of zipper early in the manufacturing process of gusseted reclosable bags, when the zipper is initially attached transversely to a bag film web and to maintain the zipper ends continuously open as the film web is formed into a bag on and about the fill tube of form, fill and seal equipment, so that a thinned out area corresponding to the bag gusset can be inserted between the zipper interlocking profiles.
A further object is to provide a method and means to engage the ends of a zipper segment in order to separate the profiles"" mating elements at the two opposite ends of the segment for a distance sufficient to receive the gusset sides.
A still further object is to maintain the profile ends of a zipper segment open and separated from each other from the initial opening thereof, while the zipper segment is moved onto a bag film web, while the bag film web with attached zipper is moved into position about the fill tube of an FFS apparatus, and until the thinned areas of the gusset sections of a bag formed from the bag film web material are tucked into the space between the opened zipper elements.
A preferred method to achieve the above objectives is to start with traditional mated zipper profiles, use a separator to separate the mated elements, then close the central part of the zipper segment while leaving each pair of ends open. The zipper may have flanges adjacent one or both sides of the profiles and leading edges of the zipper profile flanges may be tacked or peel sealed together adjacent the locked portion of the zipper segment to prevent side slippage.
The thusly prepared segment of zipper is then moved into position where it transversely overlies the bag film web to which it is sealed. During and after this attachment of the zipper to the bag film web the profiles at the separated ends of the zipper are maintained apart by guides until this portion of bag film web moves down over and around the fill tube and is formed into a reclosable bag.
These and other objects and advantages are attained by providing a method and apparatus for a vertical form fill and seal (VFFS) machine, wherein a segment of zipper having mated profiles has its mating elements, separated and then re-closed only in the central portion of the segment, leaving the profiles at the opposite ends of the segment open and separated. This prepared length of zipper is then positioned to overlie a bag film web transverse to a moving direction of the web with the open ends of the zipper segment adjacent to thinned gusset areas of the bag film web. Guides are provided to maintain the profiles at the ends of the zipper segment separated until the bag film web is moved down over and around a fill tube where it is formed into a reclosable bag.